CN104280534B - Concrete stress based on the simulation of thin sight group structure relaxes character Forecasting Methodology - Google Patents

Abstract

The invention belongs to field of civil engineering, particularly, relate to a kind of concrete stress based on the simulation of thin sight group structure and to relax character Forecasting Methodology.Concrete stress based on the simulation of thin sight group structure relaxes character Forecasting Methodology, and step is as follows: (1), coagulation local soil type to be formed point and ratio qualification; (2), each single composition sample preparation; (3), each single composition sample carries out stress relaxation test respectively; (4) the stress relaxation model of each single composition sample, is set up; (5), inverting obtains the stress relaxation parameter of single composition sample; (6), concrete sample is by the random geometry modeling of component ratio; (7), the stress relaxation character computational prediction of concrete sample.The present invention can simulate the actual constituent composition situation of actual concrete works, is not limited only to laboratory yardstick; Have wide range of applications.

Description

Concrete stress based on the simulation of thin sight group structure relaxes character Forecasting Methodology

Technical field

The invention belongs to field of civil engineering, particularly, relate to a kind of concrete stress based on the simulation of thin sight group structure and to relax character Forecasting Methodology.

Background technology

At the internal stress that calculating mass concrete causes because of temperature variation, and utilize in in-situ observed data of a dam analytical structure stress, concrete Stress relaxation is all very important.Stress relaxation also affects and conjugates because shrinking the cracking of reinforced concrete that causes and hyperstatic structure because of bearing the stresses re-distribution caused.Concrete stress relaxation refers to that material is under constant strain effect, the character that stress increases in time and decays.The reason of generation stress relaxation is the thermal motion due to material, makes distortion change plastic yield into by elastic deformation is all or part of, thus reduces the corresponding stress of elastic deformation.Therefore, concrete stress relaxation character is a very important problem for engineering stability.

Domestic and international is at present a difficult point for concrete stress slackness Quality Research, and be the little test block stress relaxation test based on laboratory mostly, size is generally at below 50cm.Due to the impact of size effect, the test findings of the little test block stress relaxation test in laboratory is difficult to be applied in Practical Project.

For this reason, the invention provides a kind of concrete stress based on the simulation of thin sight group structure to relax character Forecasting Methodology.This method first obtains often kind of group by test and forms the stress relaxation character of dividing, again according to the ratio that one-tenth various in rock is grouped into, calculate concrete integrated stress by method for numerical simulation to relax mechanical property, be expected to obtain result preferably in the prediction of concrete works stress relaxation.

The present Research of current domestic dependent Concrete stress relaxation character research method is as follows:

1, " concrete elastic modulus, creep degree and stress relaxation coefficient " literary composition describe propose modulus of elasticity of concrete, creep degree and stress relaxation coefficient a set of computing formula (see " Journal of Hydraulic Engineering " the 9th phase in 1985, author: Zhu Baifang), the method does not consider that coagulation local soil type forms the impact of point ratio, is a kind of computing method of experimental formula;

2, " stress relaxation of mass concrete " literary composition describes and draws relaxation test curve by the relaxation test of mass concrete sealed test piece, compare with various coefficient of relaxation computing method acquired results, recommend good coefficient of relaxation computing method. (see " Journal of Hydraulic Engineering " the 1st phase in 1989, author: Huang Guoxing, Deng), the sample dimensions of the method is the cylindrical of φ 15 × 45cm, but is confined to the stress relaxation character that can only reflect the little test block in laboratory;

3, " development of concrete early stage restraint stress and stress relaxation " literary grace temperature stress testing machine of imitated exploitation, is studied the development of concrete spontaneous restraint stress under 100% single shaft constraint condition and early stage stress relaxation.(see " Tsing-Hua University's journal (natural science edition) " the 3rd phase in 2010, author: Li Fei, Deng), the test specimen of this article is the long 1000mm of casting on flat, cross section is the beam specimen of 100mm × 100mm, but does not also consider that coagulation local soil type forms the impact of point ratio.

Summary of the invention

For overcoming the deficiencies in the prior art, the invention provides a kind of concrete stress based on the simulation of thin sight group structure and to relax character Forecasting Methodology.

For achieving the above object, the present invention adopts following technical proposals:

Concrete stress based on the simulation of thin sight group structure relaxes character Forecasting Methodology, and step is as follows:

(1), coagulation local soil type formation is divided and ratio qualification

(2), each single composition sample preparation

(3), each single composition sample carries out stress relaxation test respectively

(4) the stress relaxation model of each single composition sample, is set up

(5), inverting obtains the stress relaxation parameter of single composition sample

(6), concrete sample is by the random geometry modeling of component ratio

(7), the stress relaxation character computational prediction of concrete sample.

Relative to prior art, the present invention has following beneficial effect:

1, based on the stress relaxation character of single composition sample and group structure component ratio, calculate the stress relaxation character obtaining concrete sample, the actual constituent composition situation of actual concrete works can be simulated, be not limited only to laboratory yardstick;

2, this inventive method can be widely used in the mechanical performance of concrete research in the fields such as building, water power, traffic, the energy, has wide range of applications.

Accompanying drawing explanation

Fig. 1 to relax character Forecasting Methodology schematic flow sheet based on the concrete stress of thin sight group structure simulation;

Fig. 2 is stress relaxation curve character schematic diagram;

Fig. 3 is Burgers model schematic;

Fig. 4 is Xiyuan Model schematic diagram;

Fig. 5 is the grid cell stochastic distribution schematic diagram of concrete square sample.

Embodiment

As shown in Figure 1, the concrete stress based on the simulation of thin sight group structure relaxes character Forecasting Methodology, and step is as follows:

1, coagulation local soil type formation is divided and ratio qualification, and concrete grammar is as follows:

Find out that concrete group of formation is divided and nominal mix proportion, as the ratio foundation of geometric grid modeling;

Such as: certain concrete sample nominal mix proportion is: cement: flyash: sand: stone=0.2:0.1:0.2:0.5; For another example: certain concrete sample nominal mix proportion is: sand-cement slurry: coarse aggregate=0.5:0.5;

2, each single composition sample preparation, concrete grammar is as follows:

Gathering each single composition sample, to be processed into diameter respectively with the ratio of height be the cylindrical sample of 1:2, requires that the irregularity degree deviation of cylindrical sample both ends of the surface is ± 0.05 millimeter, to eliminate the impact of sample discreteness; Also the square sample of 150mm × 150mm × 150mm or larger sized sample can be prepared into;

3, each single composition sample carries out stress relaxation test respectively, and concrete grammar is as follows:

Triaxial rheometer is adopted to carry out the stress relaxation test of single shaft or multiaxis; Confined pressure and axial strain applying level can adjust according to the concrete instantaneous mechanics experimental result of reality, usually, and confined pressure σ ₃desirable 0 ~ 50MPa, axial strain ε ₁60% ~ 90% of the corresponding axial strain of instantaneous compressive strength of can materialsing;

Such as: the sample making a diameter 50mm height 100mm, is placed in flow graph and tests, first apply confined pressure σ ₃=5MPa, then applies axial strain ε ₁and keep constant, continue loading 3 ~ 15 days, observe and record axial stress σ ₁with transverse stress σ ₃, observation σ ₁~ t relation curve and specimen broke situation;

4, set up the stress relaxation model of each single composition sample, concrete grammar is as follows:

According to the stress relaxation test curve (see Fig. 2) of single composition sample, analyze Relaxation Characteristics, set up corresponding stress relaxation mechanics model;

If stress relaxation curve shows complete relaxation property, namely stress increases in time and is reduced to 0 gradually, can select Burgers model, see Fig. 3; If stress relaxation curve shows incomplete relaxation property, namely stress increase in time be reduced to gradually be not 0 constant, can Xiyuan Model be selected, see Fig. 4;

The stress relaxation equation of Burgers model is:

$\mathrm{\σ}={\mathrm{\ϵ}}_0\·\frac{q_2}{p_2(a_1-a_2)}[(\frac{q_1}{q_2}-a_2)\·\exp (-a_{2}t)-(\frac{q_1}{q_2}-a_1)\·\exp (-a_{1}t)]$

The stress relaxation equation of Xiyuan Model is:

$\mathrm{\&sigma;}=\left\{\begin{array}{cc}(E_0-\frac{E_1{E}_0}{E_1+E_0})\&CenterDot;{\mathrm{\&epsiv;}}_0\exp (-\frac{E_0+E_1}{{\mathrm{\&eta;}}_1}t)+\frac{E_1{E}_0{\mathrm{\&epsiv;}}_0}{E_0+E_1}& \mathrm{\&sigma;}<{\mathrm{\&sigma;}}_s\\ \frac{q_2{\mathrm{\&epsiv;}}_0}{p_2(a_1-a_2)}[(\frac{q_1}{q_2}-a_2)\&CenterDot;\exp (-a_{2}t)-(\frac{q_1}{q_2}-a_1)\&CenterDot;\exp (-a_{1}t)]+{\mathrm{\&sigma;}}_s& \mathrm{\&sigma;}\&GreaterEqual;{\mathrm{\&sigma;}}_s\end{array}\right.$

Wherein, $\begin{array}{c}{a}_1=\frac{p_1+\sqrt{p_1^2-4p_2}}{2p_2},a_2=\frac{p_1-\sqrt{p_1^2-4p_2}}{2p_2},\\ p_1=(\frac{{\mathrm{\&eta;}}_2}{E_0}+\frac{{\mathrm{\&eta;}}_2}{E_1}+\frac{{\mathrm{\&eta;}}_1}{E_1}),p_2=\frac{{\mathrm{\&eta;}}_1{\mathrm{\&eta;}}_2}{E_0{E}_1},q_1={\mathrm{\&eta;}}_2,q_2=\frac{{\mathrm{\&eta;}}_1{\mathrm{\&eta;}}_2}{E_1}\end{array}$

5, inverting obtains the stress relaxation parameter of single composition sample, and concrete grammar is as follows:

According to the stress relaxation model of above-mentioned foundation, least square method parameter inversion method is adopted to obtain the stress relaxation parameter of single composition sample; Namely by constantly adjusting mechanics parameter, calculated curve is made to approach trial curve gradually, if calculating calculated curve and trial curve by multi-Step Iterations coincide better, error of fitting, within the scope of setting, namely thinks that this parameter is final required stress relaxation parameter;

6, concrete sample is by the random geometry modeling of component ratio, and concrete grammar is as follows:

According to the physical dimension of actual concrete sample, in numerical software, set up corresponding geometric model, and subdivision grid, size of mesh opening is less than 1mm; According to the difference of concrete sample composition, grid cell is divided into different material groupings, the material of each grid cell divides into groups to arrange at random, but ensures that the overall quantity of all grid cells forms the ratio of dividing according to group and distributes;

Such as, a kind of concrete sample forms point A, B, a C by three kinds different groups and forms, A:B:C=5%:75%:20%; As shown in Figure 5, A composition is represented by green cell, and B component is represented by red units, and C composition is represented by blue cell, grid cell stochastic distribution in overall space of often kind of composition, but the grid cell of three kinds of compositions sum equals the number of meshes of whole sample;

7, the stress relaxation character computational prediction of concrete sample, concrete grammar is as follows:

Stress relaxation model and the stress relaxation parameter of single composition sample above-mentioned steps obtained are applied in the grid model of concrete sample, stress relaxation calculating is carried out with numerical software, the stress relaxation that can obtain concrete sample calculates curve, thus predicts the stress relaxation character of concrete sample.

Claims (8)

1. to relax a character Forecasting Methodology based on the concrete stress of thin sight group structure simulation, it is characterized in that, step is as follows:

(1), coagulation local soil type formation is divided and ratio qualification

(2), each single composition sample preparation

(3), each single composition sample carries out stress relaxation test respectively

(4) the stress relaxation model of each single composition sample, is set up

(5), inverting obtains the stress relaxation parameter of single composition sample

(6), concrete sample is by the random geometry modeling of component ratio

(7), the stress relaxation character computational prediction of concrete sample.

2. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, coagulation local soil type formation is divided and ratio qualification, and concrete grammar is as follows: find out that concrete group of formation is divided and nominal mix proportion, as the ratio foundation of geometric grid modeling.

3. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, each single composition sample preparation, concrete grammar is as follows: gathering each single composition sample, to be processed into diameter respectively with the ratio of height be the cylindrical sample of 1:2, the irregularity degree deviation of requirement cylindrical sample both ends of the surface is ± 0.05 millimeter, to eliminate the impact of sample discreteness; Or be prepared into the square sample of 150mm × 150mm × 150mm or larger sized sample.

4. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, each single composition sample carries out stress relaxation test respectively, and concrete grammar is as follows: adopt triaxial rheometer to carry out the stress relaxation test of single shaft or multiaxis; Confined pressure and axial strain applying the horizontal branch factually concrete instantaneous mechanics experimental result in border adjust, confined pressure σ ₃get 0 ~ 50MPa, axial strain ε ₁60% ~ 90% of the corresponding axial strain of instantaneous compressive strength of materialsing.

5. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, set up the stress relaxation model of each single composition sample, concrete grammar is as follows: according to the stress relaxation test curve of single composition sample, analyze Relaxation Characteristics, set up corresponding stress relaxation mechanics model; If stress relaxation curve shows complete relaxation property, namely stress increases in time and is reduced to 0 gradually, selects Burgers model; If stress relaxation curve shows incomplete relaxation property, namely stress increase in time be reduced to gradually be not 0 constant, select Xiyuan Model.

6. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, inverting obtains the stress relaxation parameter of single composition sample, concrete grammar is as follows: according to the stress relaxation model of above-mentioned foundation, adopts least square method parameter inversion method to obtain the stress relaxation parameter of single composition sample; Namely by constantly adjusting mechanics parameter, make calculated curve approach trial curve gradually, calculated by multi-Step Iterations, if calculated curve and trial curve coincide better, error of fitting, within the scope of setting, namely thinks that this parameter is final required stress relaxation parameter.

7. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, concrete sample is by the random geometry modeling of component ratio, concrete grammar is as follows: according to the physical dimension of actual concrete sample, corresponding geometric model is set up in numerical software, and subdivision grid, size of mesh opening is less than 1mm; According to the difference of concrete sample composition, grid cell is divided into different material groupings, the material of each grid cell divides into groups to arrange at random, but ensures that the overall quantity of all grid cells forms the ratio of dividing according to group and distributes.

8. the concrete stress based on the simulation of thin sight group structure according to claim 1 relaxes character Forecasting Methodology, it is characterized in that, the stress relaxation character computational prediction of concrete sample, concrete grammar is as follows: stress relaxation model and the stress relaxation parameter of single composition sample above-mentioned steps obtained are applied in the grid model of concrete sample, stress relaxation calculating is carried out with numerical software, the stress relaxation obtaining concrete sample calculates curve, thus predicts the stress relaxation character of concrete sample.